Valves are commonly used in devices that involve the transportation of a fluid. A typical use is to direct the fluid into one of a multitude of possible flow paths. For instance, in the field of liquid chromatography systems for laboratory use, where flow paths typically are of an inner diameter in the range of 0.25-2 mm, two-way solenoid valves are often used to direct a fluid. Examples of such valves are valves of the MTV series available from TAKASAGO Electrical Inc., Nagoya, Japan.
Solenoid valves tend to have limitations when used in applications where the fluid pressure is relatively high (such as pressures above approximately 0.5 MPa).
In addition, they are not well suited as multi flow path valves, i.e. valves with more than one inlet/outlet used at the same time.
For such applications, the use of rotary valves is well known in the art. Generally, a rotary valve has a stationary body, herein called a stator, which co-operates with a rotating body, herein called a rotor.
The stator is provided with a number of inlet and outlet ports. The ports are via bores in fluid communication with a corresponding set of orifices on an inner stator face. The inner stator face is an inner surface of the stator that is in fluid tight contact with an inner rotor face of the rotor. The rotor is typically formed as a disc and the inner rotor face is pressed against the inner stator face in rotating co-operation. The inner rotor face is provided with one or more grooves which interconnect different orifices depending on the rotary position of the rotator with respect to the stator.
Rotary valves can be designed to withstand high pressures (such as pressures above 30 MPa). They can be made from a range of materials, such as stainless steel, high performance polymeric materials and ceramics.
The number of inlets/outlets as well as the design of grooves in the rotator or the stator reflects the intended use of a specific valve.
A common type of multi-purpose valve has one inlet port (typically placed in the rotary axis of the valve) and a number of outlets ports that are placed equidistantly around the inlet port. The rotor has a single, radially extending groove that has one end in the rotary centre, thereby always connecting to the inlet, while the other end connects to any one of the outlets depending on the angular position of the rotor with respect to the stator. Such a valve is useful to direct a flow from the inlet to any of the outlets—one at a time.
More complicated arrangements are possible. For instance, it may be beneficial to allow more than one fluid to pass a valve or to allow a flow to pass the same valve more than one time. Valves have been designed that solves various situations of this kind.
An example of such a valve is the dual random access, three-way rotary valve that is described in U.S. Pat. No. 6,672,336, issued to Nichols. This valve solves the problem of allowing a first fluid to be directed either to an outlet “A” or an outlet “B”, and a second fluid to be directed either to an outlet “C” or an outlet “D”, all implemented in a single valve that permits the direction of the first fluid to be independent of the direction of the second fluid.
Another situation that may need to be solved for a flow-distributing system is when a flow shall be directed via three components in an alternating way, as illustrated in FIGS. 1 and 2.
The first component, the second component and the third component represents any components (or set of components) through which the flow should be guided, such as sensors, chromatography columns, other valves etc.
Provided that the flow direction through each component is of no importance (or is actually intended to be switched), this situation is easily solved with a conventional 4-way double-path valve, schematically shown in FIGS. 3 and 4.
However, the solution of FIGS. 3 and 4 is not useful in a case where the flow direction through one of the components—the second component in the figures—must not be altered. That situation is schematically illustrated in FIGS. 5 (which is similar to FIG. 1) and 6.
Examples (taken from the field of liquid chromatography) of components for which the flow direction is of importance, i.e. components that have different properties or different influence on the fluid depending on the flow direction, are sensors with non-symmetrical inner chambers, chromatography columns, ball valves etc.
Therefore, there is a need for a single valve that, in a first position, directs a flow:    from a source, through a first component, through a second component, through a third component and out through an outlet,    and in a second position directs the flow:    from the source, through the third component, through the second component, through the first component and out of the outlet,    while allowing the flow to pass the second component in the same flow direction in both of said first and second positions.